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Electronic and lattice properties of V/sub 2/Hf/sub 1-x/Ta/sub x/ C-15 superconductors

Journal Article · · Phys. Rev., B; (United States)
The heat capacities and magnetic susceptibilities chi (T) of the C-15 compounds V/sub 2/Hf/sub 1-x/Ta/sub x/ (T/sub c/ = 9-10 K), with x = 0.0-0.2, and V/sub 2/Ta (T/sub c/ = 3.6 K) have been measured between 1 and 350 K. Samples with x < 0.1 exhibit a heat-capacity anomaly indicative of a structural transformation. The geometric mean phonon frequencies ..omega../sub g/(T) were evaluated for these compounds and found to decrease monotonically with increasing chi (T) independent of temperature or composition. The high-temperature lattice properties of these materials and the presence or absence of a lattice transformation are explained in terms of the magnitude of their electronic density of states N/sub d/(E/sub F/) in the cubic phase. Strong electron-phonon coupling in the ternary compounds leads to large shifts in ..omega../sub g/(T) and, in some cases, to a structural transformation. The narrow range of T/sub c/ values for the ternary compounds occurs because their low-temperature lattice and electronic properties are similar, independent of whether or not a structural transformation has occurred.
Research Organization:
Argonne National Laboratory, Argonne, Illinois 60439
OSTI ID:
5004861
Journal Information:
Phys. Rev., B; (United States), Journal Name: Phys. Rev., B; (United States) Vol. 17:7; ISSN PLRBA
Country of Publication:
United States
Language:
English